Hellschreiber FAQ

Want to monitor and send Hellschreiber (Feld Hell) transissions, without using a bulky computer? Hellschreiber lets you decode Feld Hell transmissions on your iPhone iPad, and iPod Touch.
Just set your iPhone or iPad near a radio, tune in a transmission, and view the decoded text.

The slider lets you adjust the contrast of the received text. There is also a volume indicator.

You can also send Feld Hell transmissions as well! Just type in the text, and it is automatically sent. You can connect the audio output from the headphone jack to your transcewiver with your own cable.

To use this app, you need to feed the audio output from a your radio into the device.
You can do this via one of several ways:

Set the device near the radio's speaker to pick up the audio. While easy to do,
this is not ideal, as background noise can interfere with the audio, causing garbled decodes.

Plug headphones into the radio, and set one earphone near the mic. I find that with good
quality headphones, this can work extremely well.

Use the microphone input jack of your device, by obtaining an appopriate cable and
connecting the radio's line level output to the microphone input.

With the Camera Connection Kit, you can plug a USB sound input device into the iPad, and use
a patch cable between it and the radio's audio output. This is by far the best solution.

You can use the volume indicator in the upper right corner to verify that audio is getting into
your device, and that the volume level is appropriate.

If you are running iOS 7 or later, be sure to give the app permission to use the
microphone. If you denied permission, you can always give it again by following
these steps:

Open Settings app and go to "Privacy"

Select "Microphone" to get a list of all apps that have requested access to the microphone, and to control which apps have access to the microphone